build(docker): add dockerfile, along with GH Action to build it and push to ghcr

[djdembeck]

This pull request adds full Docker support for the project, enabling easy containerized deployment and persistent data storage. It introduces a production-ready Dockerfile, a docker-compose.yml for orchestration, a GitHub Actions workflow for automated Docker image builds and pushes, and updates the documentation to guide users on Docker usage. Additionally, it configures .dockerignore to optimize Docker builds by excluding unnecessary files.

Docker support and deployment:

• Added a multi-stage production Dockerfile for building and running the SvelteKit app with persistent data storage and production dependencies only.
• Introduced a docker-compose.yml file to simplify local development and deployment, with a named volume for persistent app data.
• Created a .dockerignore file to exclude development files, git metadata, and other unnecessary files from Docker images, improving build efficiency.

CI/CD automation:

• Added a GitHub Actions workflow (.github/workflows/docker-build.yml) to automatically build and push Docker images to GitHub Container Registry on pushes to main or manual dispatch.

Documentation:

• Updated README.md with a new Docker section, providing instructions for building, running, and persisting data using Docker and Docker Compose.